1. Field of the Invention
The present invention relates to a driving apparatus for a plasma display panel.
2. Description of Related Art
In recent years, with the trend of increasing the size of display devices, the need for thinner display devices has increased, and a variety of thin display devices have been brought into practical use. An AC (alternate discharge) type plasma display panel (hereinafter referred to as xe2x80x9cPDPxe2x80x9d) has drawn attention as one of such thin display devices.
The AC type PDP comprises a group of row electrode pairs (sustain electrode pairs) arranged on the inner surface of one of glass substrates opposing each other with a discharge space interposed therebetween, and a group of column electrodes (data electrodes) arranged on the inner surface of the other glass substrate to intersect with the row electrode pairs, and a discharge cell corresponding to one pixel is formed at each of intersections of the electrodes so that the cells are arranged as a whole in a matrix.
In such a PDP, a subfield method is used to drive the PDP to realize gradation representations. In the gradation driving according to the subfield method, one field period is divided into N subfields, in each of which a reset stage, an address stage and a simultaneous light emission sustaining discharge stage are performed in sequence. First, in the reset stage, all discharge cells are simultaneously reset for discharging to initially set all the discharge cell to either xe2x80x9clight emitting cellsxe2x80x9d or xe2x80x9cnon-light emitting cells.xe2x80x9d Also, in the address stage, the discharge cells are selectively set to xe2x80x9clight emitting cellsxe2x80x9d or xe2x80x9cnon-light emitting cellsxe2x80x9d in accordance with pixel data corresponding to an input video signal. Further, in the simultaneous light emission sustaining discharge stage, only discharge cells which have been set to the xe2x80x9clight emitting cellsxe2x80x9d are repetitively discharged to sustain their discharge light emitting states. A sequence of these operations are performed in each subfield to realize a half-tone luminance display corresponding to the input video signal.
In the half-tone luminance display as mentioned, the number of times the discharge cells are discharged to sustain the light emitting state depends on the weighting applied to each subfield. In addition, the setting of the address stage is relied on to determine whether or not the light emission sustaining discharge is performed or not in each subfield. In this way, a light emitting period and a non-light emitting period are formed in a display period of one field corresponding to an input video signal. In other words, as an input video signal has a higher luminance, the light emitting period occupies a larger proportion within one field period. Conversely, as the input video signal has a lower luminance, the non-light emitting period occupies a larger proportion within one field period.
Here, power consumed by a PDP varies depending on the light emitting period, i.e., the number of xe2x80x9clight emitting cellsxe2x80x9d and the number of times these xe2x80x9clight emitting cellsxe2x80x9d emit light. More specifically, the power consumption becomes minimum when all the discharge cells are set to xe2x80x9cnon-light emitting cellsxe2x80x9d and becomes maximum when all the discharge cells are set to xe2x80x9clight emitting cells.xe2x80x9d For this reason, a power supply circuit for use in driving a PDP should be set to have its current supply capability which is assumed to be required when all the discharge cells are set to xe2x80x9clight emitting cells.xe2x80x9d
However, since an average luminance level of a video signal is typically about 30 percent of a maximum luminance level, the power supply circuit has an excessive margin in the current supply capability in a normal video display state. Thus, the conventional PDP driver has a problem in that the power supply circuit itself is large in scale due to the surplus current supply capability possessed thereby.
The present invention has been made to solve the problem mentioned above, and an object of the present invention is to provide a driving apparatus of a plasma display panel which is capable of reducing the scale of the driver itself while suppressing the power consumption.
The present invention provides a driving apparatus of a plasma display panel having a plurality of discharge cells arranged in matrix, wherein a unit display period is divided into a light emitting period and a non-light emitting period in accordance with an input video signal for driving the plasma display panel, such that the discharge cells are driven to repeatedly emit light only during the light emitting period to provide a display at a half-tone luminance. The driver comprises power consumption control means for adding a value corresponding to power consumed during the non-light emitting period to an average luminance level of the input video signal to control power consumption of the plasma display panel based on the average power consumption.